How To Use Bomtable For Counting Hangers In Autocad Mep
In AutoCAD MEP, a Bill of Materials (BOM) table is your primary tool for automating the quantification of elements like pipe hangers directly from your intelligent model. It works by querying the model’s database for parts that match specific criteria you define, such as part type, system, or size, and then compiling their counts into a structured table. For hanger counting, this process begins with ensuring your model is built correctly; every hanger must be an actual MEP part, typically a non-flanged component like a clevis, trapeze, or spring hanger, placed from the Parts Browser and connected to the piping system. If you’ve manually drawn hanger geometry as generic lines or blocks, the BOM tool will not recognize them, so using the correct MEP hanger parts from the outset is non-negotiable for accurate automated counting.
To generate a hanger count, you initiate the process by typing `BOM` or navigating to the MEP tab and clicking the Parts List panel’s Parts List button. This opens the Parts List dialog, which is the control center for your query. Here, you define the scope: you can choose to generate the BOM from the entire current drawing, from selected objects only, or from a specific view or work set. For a project-wide hanger tally, selecting the entire drawing is common, but for a focused count on a particular floor or system, using a selection set of relevant pipes and their associated hangers is more precise and often faster. The dialog then allows you to filter the parts that will be included in the final table.
The critical step for hanger-specific counting is setting up the filter criteria within the Parts List dialog. You add a new filter rule and set the first condition to `Category` equals `Hanger`. This single rule instructs AutoCAD MEP to scan the model and extract only those parts whose category is defined as a hanger in the Parts Database. You can further refine this by adding conditions like `System Type` equals `Hydronic Piping` or `Size` between specific values, which is invaluable for breaking down counts by pipe diameter or service. For example, you might create one BOM for all 1-2″ hydronic hangers and another for 2-1/2″ and above to reflect different design requirements or procurement packages.
Once your filters are set, clicking OK generates the BOM table in the drawing. The table’s columns are determined by the properties you choose to include in the Parts List dialog’s display settings. For hanger counts, essential columns are `Part Name` (to distinguish between clevis, trapeze, etc.), `Size`, `System`, and `Count`. The `Count` column is the automated total for each unique combination of the other displayed properties. If you need a simple total of all hangers regardless of type, you would ensure only the `Part Name` column is included, and the table will list each hanger part type with its individual count, which you can then sum manually or with a spreadsheet export. The table is a dynamic AutoCAD table object; you can edit its text style, merge cells, or adjust column widths for clarity in your construction documents.
A common point of confusion arises when expected hangers do not appear in the BOM output. This usually stems from one of three issues: the hanger part in the model is not actually assigned a “Hanger” category in the Parts Database, the part was inserted as a non-MEP object (like a block), or the filter criteria inadvertently exclude it. To troubleshoot, use the `AECCTAGS` command or the Properties palette to inspect a hanger in the model and verify its `Category` property. You must also ensure your project’s Parts Database is correctly configured and loaded; the database dictates the available categories and part definitions. If your standard hanger part is missing the “Hanger” category, you or your CAD manager must edit the `.xml` part definition file to assign it, a task requiring administrative rights and database management knowledge.
For holistic project management, you often need more than a single hanger count. The true power of the BOM tool lies in creating multiple, specialized tables from the same model. You might generate one BOM table listing hangers by system and size for the mechanical contractor, and another that groups them by location or zone for the installation crew. To do this efficiently, save your filter setups as named Parts List templates within the dialog. This allows you to regenerate updated counts with a single click as the design evolves, ensuring your schedules always reflect the current model without re-building the query logic each time. Remember, the BOM is only as accurate as the model it reads; any hanger added, deleted, or modified in the 3D model requires a BOM regeneration to update the count.
Finally, consider the workflow integration. A best practice is to place your finalized BOM tables on a dedicated sheet, often titled “Pipe Support Schedule” or “Hanger Summary.” Link this sheet to your overall construction document set. Before finalizing, always cross-check a sample of the BOM counts against a manual selection count using the `QSELECT` command filtered by part category to catch any database anomalies. The process of using BOM tables for hanger counting embodies the shift from 2D manual takeoffs to model-based quantification. It reduces human error, saves significant time on large projects, and creates a direct, auditable link between the design intent in the model and the material procurement list. The key takeaway is to treat your MEP model as a database: build it with intelligent parts, understand your Parts Database, master the filter logic in the Parts List tool, and you will transform hanger counting from a tedious manual chore into a reliable, automated reporting function.
